NUL undeclared- first use in this function

Question

From the web I understand that C contains `NUL` keyword. But while compiling I get an error ``` NUL undeclared first use in this function' ``` My code fragment: ``` for (;;) { char ch = (*pzDest = *pzSrc); if (ch == NUL) break; if (ch == ':') { *pzDest = NUL; break; } pzDest++; pzSrc++; } ``` Any idea why I get this error?

Accepted Answer

There's NULL and then there's NUL.

NULL is defined in stddef.h, is used very widely, and is a reference to a null pointer.

NUL is different - it is the first character in the standard ASCII character set, and more importantly, it is not a standard macro. You may have to define it yourself.

To define NUL, do:

```
#define NUL '\0'
```

NUL undeclared- first use in this function

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